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Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061
ABSTRACT
Near infrared reflectance spectroscopy analysis of forages for CP, ADF, NDF, and minerals was compared with wet chemistry results. Infrared analysis was conducted with a NEO-Tech 51A where spectral equations had been transferred by the vendor from master calibrations. These calibrations were based upon microwave drying of feed samples and grinding through a cyclone mill. Our forage testing laboratory routinely tests by oven drying at 60°C and grinding with a Wiley mill through a 2-mm screen. Protein and ADF analyses were conducted on 66 corn silage, hay crop silage, and hay samples. Coefficients of determination for oven drying-wet chemistry and microwave-infrared, oven drying-wet chemistry and oven drying-infrared, and microwave-infrared and oven drying-infrared analysis were: .90, .93, and .98 for crude protein and .92, .94, and .96 for ADF. Infrared results were compared with wet chemistry CP and ADF for 265 corn silage, hay, and hay crop silage samples. Coefficients of determination were .97 for CP and .95 for ADF with standard errors of prediction of .92 and 1.98. The respective correlation coefficients for corn silage, hay crop silage, and hay were .94 and .73; .95 and .92; and .73 and .74. Although standard errors of prediction were low for all minerals, coefficients of determination were above .80 for Ca and K.
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